Romain Grosjean was quickest as heavy rain hit the opening practice session for the British Grand Prix at Silverstone.
Conditions were wet from the outset, and steadily worsened. That meant that the 1m56.552s lap that Lotus driver Grosjean produced after 37 minutes proved to be the fastest anyone could manage all morning. Demonstrating how tricky the track was, Grosjean took to the grass at Becketts just after setting his benchmark time.
Daniel Ricciardo was among the initial pacesetters and remained second for Toro Rosso, 0.275 seconds behind Grosjean.
Lewis Hamilton led the home contingent for McLaren in third, followed by Sergio Perez's Sauber, Felipe Massa's Ferrari, and Red Bull driver Mark Webber, who also took several turns on top early on.
Although Kamui Kobayashi was only seventh in the times, he was among the most spectacular to watch on the wet track, managing to keep his Sauber on the road most of the time despite some slides. Team-mate Perez was one of several to have a harmless spin - although his incident could have collected Grosjean.
Marussia's Timo Glock and HRT test driver Dani Clos also looped their cars, but despite the conditions, everyone managed to avoid the barriers.
Unusually for a wet session, the majority of the field came out for some concerted running. Only the Force Indias and Ferrari's Fernando Alonso decided against flying laps.
Pos Driver Team Time Laps 1. Romain Grosjean Lotus-Renault 1m56.552s 13 2. Daniel Ricciardo Toro Rosso-Ferrari 1m56.827s + 0.275 10 3. Lewis Hamilton McLaren-Mercedes 1m57.174s + 0.622 6 4. Sergio Perez Sauber-Ferrari 1m57.664s + 1.112 11 5. Felipe Massa Ferrari 1m58.119s + 1.567 7 6. Mark Webber Red Bull-Renault 1m58.463s + 1.911 7 7. Kamui Kobayashi Sauber-Ferrari 1m58.483s + 1.931 19 8. Michael Schumacher Mercedes 1m58.493s + 1.941 10 9. Nico Rosberg Mercedes 1m58.942s + 2.390 8 10. Jean-Eric Vergne Toro Rosso-Ferrari 1m59.076s + 2.524 12 11. Sebastian Vettel Red Bull-Renault 1m59.414s + 2.862 11 12. Vitaly Petrov Caterham-Renault 1m59.614s + 3.062 9 13. Valtteri Bottas Williams-Renault 1m59.733s + 3.181 7 14. Heikki Kovalainen Caterham-Renault 1m59.787s + 3.235 10 15. Pastor Maldonado Williams-Renault 2m00.125s + 3.573 5 16. Kimi Raikkonen Lotus-Renault 2m00.253s + 3.701 6 17. Jenson Button McLaren-Mercedes 2m01.834s + 5.282 6 18. Timo Glock Marussia-Cosworth 2m01.835s + 5.283 6 19. Pedro de la Rosa HRT-Cosworth 2m04.341s + 7.789 9 20. Dani Clos HRT-Cosworth 2m05.022s + 8.470 11 21. Charles Pic Marussia-Cosworth 2m11.760s + 15.208 6 22. Fernando Alonso Ferrari 4 23. Paul di Resta Force India-Mercedes 3 24. Jules Bianchi Force India-Mercedes 1 All Timing Unofficial